It really depend on the player in question. It's not uncommon to see guys drafted in the 8th round or later getting $750,000 - $1,000,000 signing bonus, which is late 1st round/sandwich round/early second round type money.

There is no hard number, just a number MLB recommends. As for what MLB's slot recommendations, the best I could find is this, which shows the average signing bonus the past few years for the 11th, 57th, 89th, 123th and 153th overall picks (which are the Rangers' first five picks this year).